I love my Kata bag (a DR-467)

Mine dream bag is pretty much what I have:
-Laptop capable (at least 15.4")
-Backpack (less obvious that it contains things worth more than any car I've ever owned. Maybe more than every car I've ever owned combined--how's that for priorities?)
-Waterproof cover
-Velcro, customizable compartments
-Waist strap for longer hikes
-Carry-on compatible

I would improve on my bag by adding
-tripod holder (maybe even just nylon straps at the bottom)
-removable pouches to fit on the waist strap (like holsters--one of my family nicknames is John Wayne III), one at least big enough to fit a 70-200 f/2.8
-some kind of stretchy, grippy mesh on the back of the bag to stick things in for a few minutes when I need to put them somewhere without opening the bag. I'm imagining something like the camo nets snipers use to stick local foliage in their helmets, only rubber coated and stretchy/big enough to even let in a smallish lens, my gloves, or a flash.

http://www.dreambagchallenge.com/

Thought I should post this, its a competition to design your own camera bag and if you win it gets made! You also get 5000$ of canon equipment to either return or sell to a friend!